Re: [PATCH v3 07/33] drm/vkms: Introduce configfs for plane name

José Expósito
2025-12-29T15:52:02Z

Hey Louis,

On Mon, Dec 22, 2025 at 11:11:09AM +0100, Louis Chauvet wrote:
> Planes can have name, create a plane attribute to configure it. Currently
> plane name is mainly used in logs.
>
> Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>
> ---
> Documentation/ABI/testing/configfs-vkms | 6 +++++
> Documentation/gpu/vkms.rst | 3 ++-
> drivers/gpu/drm/vkms/vkms_configfs.c | 43 +++++++++++++++++++++++++++++++++
> 3 files changed, 51 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/ABI/testing/configfs-vkms b/Documentation/ABI/testing/configfs-vkms
> index 0beaa25f30ba..6fe375d1636f 100644
> --- a/Documentation/ABI/testing/configfs-vkms
> +++ b/Documentation/ABI/testing/configfs-vkms
> @@ -103,6 +103,12 @@ Description:
> Plane type. Possible values: 0 - overlay, 1 - primary,
> 2 - cursor.
>
> +What: /sys/kernel/config/vkms/<device>/planes/<plane>/name
> +Date: Nov 2025
> +Contact: dri-devel@lists.freedesktop.org
> +Description:
> + Name of the plane.
> +
> What: /sys/kernel/config/vkms/<device>/planes/<plane>/possible_crtcs
> Date: Nov 2025
> Contact: dri-devel@lists.freedesktop.org
> diff --git a/Documentation/gpu/vkms.rst b/Documentation/gpu/vkms.rst
> index 1e79e62a6bc4..79f1185d8645 100644
> --- a/Documentation/gpu/vkms.rst
> +++ b/Documentation/gpu/vkms.rst
> @@ -87,10 +87,11 @@ Start by creating one or more planes::
>
> sudo mkdir /config/vkms/my-vkms/planes/plane0
>
> -Planes have 1 configurable attribute:
> +Planes have 2 configurable attributes:
>
> - type: Plane type: 0 overlay, 1 primary, 2 cursor (same values as those
> exposed by the "type" property of a plane)
> +- name: Name of the plane. Allowed characters are [A-Za-z1-9_-]
>
> Continue by creating one or more CRTCs::
>
> diff --git a/drivers/gpu/drm/vkms/vkms_configfs.c b/drivers/gpu/drm/vkms/vkms_configfs.c
> index 506666e21c91..989788042191 100644
> --- a/drivers/gpu/drm/vkms/vkms_configfs.c
> +++ b/drivers/gpu/drm/vkms/vkms_configfs.c
> @@ -324,10 +324,53 @@ static ssize_t plane_type_store(struct config_item *item, const char *page,
> return (ssize_t)count;
> }
>
> +static ssize_t plane_name_show(struct config_item *item, char *page)
> +{
> + struct vkms_configfs_plane *plane;
> + const char *name;
> +
> + plane = plane_item_to_vkms_configfs_plane(item);
> +
> + scoped_guard(mutex, &plane->dev->lock)
> + name = vkms_config_plane_get_name(plane->config);
> +
> + if (name)
> + return sprintf(page, "%s\n", name);
> + return sprintf(page, "\n");
> +}
> +
> +static ssize_t plane_name_store(struct config_item *item, const char *page,
> + size_t count)
> +{
> + struct vkms_configfs_plane *plane;
> + size_t str_len;
> +
> + plane = plane_item_to_vkms_configfs_plane(item);
> +
> + // strspn is not lenght-protected, ensure that page is a null-terminated string.
> + str_len = strnlen(page, count);
> + if (str_len >= count)
> + return -EINVAL;

I made a very quick review of v3 and I'm sending the initial issues I found, but I'd need
to do a deeper review.

This check is preventing me to set the name. For example, running:

$ echo "planename" | sudo tee /sys/kernel/config/vkms/gpu1/planes/plane0/name

Fails because str_len = 10 and count = 10. Does the same happen on your side?

Jose

> +
> + if (strspn(page, "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_-") != count - 1)
> + return -EINVAL;
> +
> + scoped_guard(mutex, &plane->dev->lock) {
> + if (plane->dev->enabled)
> + return -EBUSY;
> +
> + vkms_config_plane_set_name(plane->config, page);
> + }
> +
> + return (ssize_t)count;
> +}
> +
> CONFIGFS_ATTR(plane_, type);
> +CONFIGFS_ATTR(plane_, name);
>
> static struct configfs_attribute *plane_item_attrs[] = {
> &plane_attr_type,
> + &plane_attr_name,
> NULL,
> };
>
>
> --
> 2.51.2
>